Détails:Flight CI-012, encountered moderate turbulence at flight level 330. The airplane subsequently departed controlled flight and sustained damage to the left and right outboard elevator skin assemblies, portions of which separated from the airplane. The airplane continued on and landed uneventfully at Anchorage, AK.

Probable Cause:

PROBABLE CAUSE: "The flight control force characteristics of the MD-11 airplane in high altitude cruise flight. The upset was induced by a moderate lateral gust and was exacerbated by excessive control deflections. Contributing to the incident was a lack of pilot training specific to the recovery from high altitude, high speed upsets in the MD-11."

Sources:

» NTSB/AAR-94/02

Opérations de secours

NTSB issued 3 Safety Recommendations

Issued: 17-MAR-1994

To: FAA

A-94-37

REQUIRE DOUGLAS AIRCRAFT COMPANY TO ADVISE MD-11 OPERATORS OF THE POTENTIAL FOR DAMAGE TO THE COMPOSITE ELEVATORS IF THE AIRPLANE IS OPERATED BEYOND THE LIMITS OF THE DESIGN BUFFET BOUNDARY, AND TO INFORM THESE OPERATORS THAT PILOTS MIGHT PERCEIVE THE STALL BUFFET (AND SUBSEQUENT LOSS OF CONTROL) ENCOUNTERED DURING HIGH ALTITUDE, HIGH SPEED UPSETS AS SEVERE TURBULENCE. (Closed - Acceptable Action)

Issued: 17-MAR-1994

To: FAA

A-94-38

REQUIRE INSPECTION, USING NONDESTRUCTIVE ULTRASOUND "A" SCAN INSPECTION TECHNIQUES, OF COMPOSITE ELEVATORS ON MD-11 AIRPLANES THAT ARE KNOWN TO HAVE BEEN OPERATED OUTSIDE THE DESIGN BUFFET BOUNDARY. (Closed - Acceptable Action)

Issued: 17-MAR-1994

To: FAA

A-94-39

ESTABLISH CERTIFICATION REQUIREMENTS FOR FLIGHT CONTROL HANDLING CHARACTERISTICS, SUCH AS STICK FORCE PER G LIMITS, AND REQUIRE FLIGHT DEMONSTRATIONS TO ENSURE THAT PILOTS CAN SAFELY RECOVER FROM ABRUPT HIGHT ALTITUDE, HIGH SPEED UPSETS IN TRANSPORT-CATEGORY AIRPLANES. (Closed - Acceptable Action)